Contrarian Micro Textures has announced their findings relating to research they conducted on solar reflectance that has determined stainless steel roofs can provide a significant reduction in global warming. Further, the sustainably efficient solar reflectance of stainless steel, combined with its very low emission of infrared energy, create more energy efficient buildings. While it is theoretically possible to offset global warming completely by roofing enough buildings in stainless steel, the real solution to the problem would include further conservation measures as well. The point being that stainless steel roofs offer a meaningful contribution towards cooling the planet.

Stainless steel is an extraordinarily efficient reflector of solar radiation, making it an ideal material for building construction, particularly roofing. While initial solar reflectance of white painted metal surfaces can achieve the same degree of reflectance as stainless steel, painted surfaces lose up to 5% of their solar reflectance each year, due to oxidation. An oxidized surface tends to convert solar energy to infrared energy, which heats up the atmosphere. Since stainless steel does not oxidize, it retains its solar reflectance efficiency over time. Therefore stainless steel provides a much greater offset to global warming in the long run compared to white painted metals or membrane products that degrade over time. Beyond effectively cooling the planet, stainless steel roofs and wall systems conserve energy. In fact, stainless steel contributes an insulation value to an exterior cladding system.

During daylight hours the Sun bombards the Earth with solar radiation, averaging 395 Watts per meter squared for 85% of the planet. About a third of this radiation is reflected by the Earth's surface. The remainder gets converted to infrared energy (heat), which gets absorbed and re-emitted by greenhouse gases. The effect of this is to warm the surface and the troposphere of the Earth. The physics here is pretty simple, carbon in the atmosphere, whether it's generated naturally by the Earth or by man-made means, serves to trap infrared energy. If we are able to generate less heat through energy conservation, improvement in the global warming phenomenon can be achieved. However, conservation alone cannot solve the problem. We must rely on reflective materials to make a substantial contribution in order to completely offset global warming.

Any human who dresses for a hot sunny day will prefer a white shirt to a black one in order to be comfortable. We offer another example of a natural species on the Earth that has adapted to living in a region of the earth where solar radiation is intense. Clad in a reflective skin, the Saharan Silver Ant is able to function effectively in the midday sun. Other species are unable to operate in full vigor during full sunlight, but this creature manages to reflect solar radiation very efficiently. Building design professionals can take a lesson from the Saharan Silver Ant in creating buildings that are likewise not reactive to the midday sun. The world will be cooler if buildings are clad in sustainably reflective materials like stainless steel.

Stainless steel reflects substantially more solar energy without converting to infrared (heat) than asphalt or white painted metal. In fact, stainless steel absorbs only 8 Watts per meter squared (about 3% of total radiation) of infrared energy compared to 46 Watts per meter squared in the case of aged white painted metal and a whopping 122 Watts in the case of asphalt.

It's important to point out that much of the burden of the solution of reflective materials to curb global warming lies in latitudes nearer to the equator, as the angle of the Sun creates both a greater impact and a greater opportunity for effective remediation. When you consider the world's population growth and wealth generation is skewed toward countries near the equator, a large part of the burden as well as the opportunity to achieve global cooling lies between the 45th parallels North and South. It is interesting to note that if 2,000 square feet of stainless steel roofing were installed for each person on Earth, global warming would be offset completely. Highlighting the areas of Texas and Burma combined, which represent the portion of the Earth that would need to be covered in stainless steel to neutralize global warming, it is not realistic to build giant canopies over these regions no more than it is realistic to build 2,000 square feet of roofing per person. Clearly, a solution to global warming is within reach by maximizing the use of highly reflective building materials like stainless steel combined with effective conservation measures.

Because of its very low emissivity, stainless steel makes a contribution in the area of conservation as well. Assuming outside temperature of 40°C (104°F) and maintaining an interior building temperature of 20°C (68°F), half the insulation of white painted metal and a third of the insulation of asphalt is required to maintain a heat loss of 10 Watts per meter squared in the case of stainless steel. With stainless steel building panels, the owner has two very good choices. The first is to accept good performance with less insulation and therefore save expenses related to acquiring it and providing space to install it. The second, and perhaps better choice is to detail a building that is even more energy efficient using standard insulation details that are used with more common materials.

A real world example of a stainless steel roof saving energy can be found at the David Lawrence Convention Center in Pittsburgh, PA. While stainless steel was originally chosen for its durability, high recycled content and high recyclability, it stands to reason that the stainless steel roof has contributed to energy savings as well. In fact, the DLCC upgraded the building’s LEED® status from Silver to Gold, due in part to lower than expected energy consumption in the 15 – 20% range. While an engineering study concluded a natural ventilation system has been the major contributor to the building’s energy efficiency, Contrarian’s later research suggests a meaningful contribution from the stainless steel roof itself. Solar reflectance readings taken on the DLCC roof 10 years after installation, with no cleaning having ever been conducted, showed no degradation compared to a cleaned roof specimen or a new control sample. The dirt resistant InvariMatte® finish was deemed to be a factor in maintaining the roof’s energy efficiency.

Stainless steel is an undervalued building material that provides significant benefits to the building owner and represents a substantial weapon in the battle against global warming. Beyond its impressive energy performance, as a building material, stainless steel has low embodied energy compared to other construction materials including glass, carbon steel, and aluminum. Stainless steel contains at least 60% recycled content and is 100% recyclable without having to downgrade to less critical applications. Stainless steel building panels are resistant to fire, wind, hail, and corrosion. Because of its extraordinary durability and corrosion resistance, stainless steel buildings can last indefinitely, assuring low maintenance cost and a long service life.

Stainless steel is a completely appropriate building material given its durability and low maintenance cost. While the owner of a stainless-clad building benefits from these characteristics, society at large benefits from the sustainability of this versatile material. Beyond being remarkably durable, sustainability is realized from stainless steel's recycled content and recyclability.

Much has been written in recent years regarding stainless steel's recycled content. The LEED® initiative has encouraged disclosure of producers' recycling statistics. These statistics are impressive with the average global producer figure achieving 60% recycled content, according to the International Stainless Steel Forum (ISSF). The Specialty Steel Industry of North America (SSINA) states further that US producers of stainless steel operate in the 75 to 85% range. It is to the stainless steel manufacturers’ advantage to maximize the use of scrap in the process of making stainless steel. Given the growth of the use of stainless steel and its long life cycle, estimated by the American Institute of Steel Construction (AISC) to average 20-30 years for all stainless steel parts, there simply isn't enough scrap available at the present time to achieve a global statistic greater than 60%.

While these high recycled content statistics are remarkable, it's become apparent that the aspect of recyclability of stainless steel is not thoroughly understood. We address recyclability in three areas. First, stainless steel's suitability to be recycled, its likelihood of occurrence, and the quality of recycled stainless steel.

In terms of suitability for recycling, stainless steel is a no-brainer. Virtually all grades of this material can be readily melted into new heats that can meet essentially all downstream application requirements. The high melting point of stainless steel facilitates the removal of coatings and contaminants within the melting process, making for an efficient direct charge of various scrap materials, thereby minimizing the extent to which these materials need to be prepared for recycling.

The relatively high value of nickel, chrome and molybdenum units within stainless steel scrap virtually assures recycling is conducted and done so on a timely basis. Given that 60% of the world's production of stainless steel comes from scrap, there is a vast infrastructure of scrap recycling businesses around the world that facilitate the process of recycling. Specifiers of stainless steel can be confident that at some future date, when the useful life of the stainless steel parts come to an end, that the valuable resource intrinsic in the stainless steel material itself will not be wasted. Rather, the value of this discarded stainless steel part itself is worth the trouble to see that it is sold to a scrap dealer that virtually assures prompt and efficient recycling takes place.

Lastly, it seems some people are under the impression that stainless steel once recycled suffers quality degradation. This false impression may exist because quality suffers in the recycling of many other building products, including plastics, aluminum that is not de-coated, and rubber products. Again, since stainless steel at large has such a high recycled content, it is impractical to suggest the vast majority of stainless steel produced ends up in applications that can tolerate substandard quality. Once again it is the high melting point, which drives out impurities in the furnace and again in an AOD refining operation, that assures the cleanest and most sophisticated chemistries of stainless steel can be obtained using recycled scrap.

In summary, stainless steel building components are capable of being permanent as long as the building stands. There's no need to re-paint them or replace them, unless unexpected damage occurs. When the building is eventually torn down, it is virtually assured the decommissioned parts will be sent swiftly into a steel mill's melt shop to be born again into new products that will have a very long life cycle.

From Contrarian’s Website:

Our philosophy regarding architectural metals is to select a product that will last the useful life of the building with little or no maintenance. This usually results in the least long-term cost to the building owner (see Life Cycle Costing). In addition, significantly less harm can be made to the environment by using long life materials as opposed to more commonly used materials that require maintenance and replacement. Specifically, our portfolio of high performance architectural metals serves this philosophy well. Beyond offering sustainability (when properly specified and installed) these metals are, by their nature, environmentally “green” materials.

Stainless Steel

According to the Specialty Steel Industry of North America approximately 60% of the world’s stainless steel production contains recycled material. Some products will have a lower recycled content while others will be higher, based on melting location, grade and product form. Please contact a representative for details of the recycled content specific to your project. The relatively high value of stainless steel scrap assures that the bulk of discarded items are quickly re-melted and not sent to a landfill. Some recycled materials, like rubber, plastic and painted aluminum that is not de-coated, suffer quality degradation or have limitations regarding suitability for certain applications. Recycled stainless steel, however, has no such limitations. Stainless steel is extremely durable as well as stable at ambient temperatures. Stainless steel, often used in jewelry, medical implants and cookware, is harmless to living things.Since stainless alloys are extremely stable at ambient temperatures, there is no leaching or run-off. Stainless steel production in the US, as well as other advanced nations, makes use of substantial pollution control technology. While it still consumes some natural resources, as well as energy to produce, many other materials use more resources, creating a higher environmental impact. The recycled content of stainless steel produced in the United States is higher than that of most other countries.Having a favorable strength-to-weight ratio compared to most other metals, stainless can be engineered to lighter gauges, thus consuming less material.Stainless steel has substantially lower thermal conductivity than metals like aluminum and carbon steel that are more commonly used as building materials. Theoretically, a stainless steel building envelope will absorb less energy, thereby reducing the transmission of external energy (heat) to the interior spaces. In cold weather, the opposite effect of reducing the transfer of energy to the exterior would be true.

EXCERPT FROM AISC Design Guide for structural stainless steel:

Stainless steel producers use as much scrap as is available, but the material’s overall average 20 to 30 year service life limits scrap availability. In 2002, the International Stainless Steel Forum (ISSF) estimated that, internationally, the typical recycled content for all types of stainless steel was about 60%. In North America, the Specialty Steel Industry of North America (SSINA) has a downloadable LEED® statement indicating that the typical recycled content of the austenitic stainless steels is between 75-85%. Currently, in parts of the world where scrap is readily available, some producers are reporting scrapped recycled content levels up to 90%. Stainless steel is 100% recyclable and can be indefinitely recycled into new high quality stainless steel.

Aside from catastrophic damage, metallic corrosion is clearly the chief cause of metal building panel failure. When architectural metal panels corrode, there are undesirable consequences that go beyond cosmetics. Corroding panel systems will begin to leak, causing potentially significant damage to the interior of a building. Repair costs can be substantial, usually involving removal and replacement.

Studies conducted in the 1990’s by both Battelle Laboratories and the National Association of Corrosion Engineers (NACE) concurred that in the United States alone, we spend nearly $300 billion per year combating metallic corrosion. The Battelle study estimated that $100 billion of this cost can be avoided with proper material selection. This suggests that to a significant degree, we are penny wise and pound foolish with the metals we specify. It has been estimated that half of new steel production relates to replacing corroded parts. Beyond the obvious economic impact, there is a negative environmental impact as well.

In terms of architectural metal applications, life cycle costing should be taken into account when selecting materials. It's a simple case of measuring the cost of building materials that will last as long as the anticipated life of the structure and comparing those costs, in present value terms, to alternate materials that will require additional maintenance and/or replacement. Clearly, the construction industry has been operating in a mindset that maintenance and replacement of building materials is a foregone conclusion. However, in light of the extraordinary costs we bear in battling corrosion, more attention to material selection is warranted.

Since the corrosion cost studies of the 1990's some progress has been made in addressing the problem. In order to stem corrosion costs that exceed $20 billion per year with the U.S. Armed Forces, a Corrosion Policy and Oversight office was established within the Pentagon in 2003. The Defense Department also contributed to the establishment of corrosion engineering program at the University of Akron. Clearly, the U.S. Government sees opportunity to reduce costs in the military budget.

There has been a great deal of growth in recent years in the use of metal building panels, which is a welcome step in the right direction. Metal panel systems are in a category above many conventional building materials in terms of long service life at a reasonable cost. However, greater consideration needs to be given to longer lasting metals like stainless steel, zinc and copper for cladding applications on buildings with anticipated service lives that exceed 50 years. This is particularly true in coastal locations and climates where deicing salts are used. Corrosion failures of conventional metals are more prevalent in these locations due to chloride exposure. While paint systems go a long way to preserve substrate metals like carbon steel and aluminum, sheared edges and areas compromised by damage, metal forming and welding go unprotected. Provided the right grade of stainless steel is matched with the environment, as an example, corrosion is not an issue.

The construction industry has seen measurable growth in the use of more corrosion resistant metals. Just 10 years ago, a stainless steel building envelope was considered to be extravagant; reserved only for iconic buildings with exceptional budgets. Today, however, stainless steel and other corrosion resistant metals have gained acceptance for use on projects in the mainstream. What was once thought to be extravagant is now considered to have solid economic value. A stainless steel finish needs only to be cleaned periodically to last as long as the building stands. With no repainting or replacement required, the building owner gets a solid return on investment. Further, service disruptions and their related costs are avoided.

Beyond the simple math of maintenance savings from using durable materials like stainless steel, building owners get the added benefit of higher property value. While it may be difficult to put a precise value on a building with a stainless steel envelope compared to one that requires refinishing or replacement, it stands to reason that the owner has a valuable selling point when the time comes to sell. It’s similar to the residual value argument that car rental and leasing companies embraced years ago. In the old days, fleet cars were stripped down, entry level models that provided low cost transportation. In contrast, today’s fleets are more likely to include better models with higher value features that support better residual value when the vehicle is resold. Similarly, building owners should take note of residual value as they, their architects and contractors make decisions regarding construction materials.

Stainless steel is emerging as a material of choice in building construction. Its longevity is without question. Recycling statistics are impressive. Finishing methods offer substantial variety. While the majority of architectural applications of stainless steel have been for interior elements like elevators, the shift toward sustainable materials has propelled the use of stainless steel as a building envelope in recent years. In this column, we will endeavor to make designers, specifiers, fabricators and contractors more familiar with the application of stainless steel in architecture.

While we are pleased to gain the reader’s input in terms of feedback as well as suggested subject matter, we envision this column will share insight into specification guidance, energy efficiency, finishing methods, cleaning procedures, fabrication advice and other aspects of stainless steel building applications. In this very first column, we will explore the evolution of the use of stainless steel on building exteriors.

A building envelope is what separates the inside from the outside and its components include the foundation, the roof, the walls, the door and the windows. The materials used for these parts help determine the effectiveness, structural integrity and durability of the building, which stated briefly means the way that the pieces interact with one another, their connections, their fasteners and fabrications. All these pieces and their details work in conjunction to provide physical protection from the weather, the indoor climate, the air quality, the durability and the energy efficiency.

Stainless steel’s use in building envelope applications dates as far back as the 1920s. Perhaps the most prominent building from that era is the Chrysler Building. Completed in 1930, the stainless work has withstood the test of time, with maintenance limited to two cleanings (one in 1961 and another in 1995) and the replacement in 1995 of a few panels near the heating exhausts that showed evidence of pitting corrosion. Clearly, the use of such a durable material has saved the owners of this building considerable expense over the years.

Another example of stainless steel’s durability is the Saucony Mobil building, also in New York City. The accompanying photo shows a recent cleaning that was undertaken.

Completed in the mid 1950’s, the building accumulated dirt until cleaning was undertaken in 1995. This cleaning was accomplished with soap, water and cotton cloths. The finish, being somewhat coarse, facilitated the buildup of dirt on the exterior surfaces but this condition did not prevent the appearance from being 100 percent restored with traditional cleaning methods.

These fine examples of stainless steel envelopes on historic buildings underscore what true sustainability is as stainless steel offers greater residual and resale value with lower maintenance costs as it does not require repainting or resurfacing.

In addition, stainless steel requires minimal maintenance, when properly specified and installed it does not require replacement and therefore avoids service disruption which should not be undervalued.

Stainless steel lasts indefinitely without coatings that can emit volatile organic compounds (VOCs) as in painted surfaces. Stainless requires minimal maintenance and has no leaching or runoff as with less stable materials. Worldwide stainless steel is 60% recycled, in the United States the figure is 80%, so a truly green, sustainable product that when used appropriately will garner LEED® certification points. In addition when the building is no longer in service it is highly likely that the materials will be recycled, the result is a sustainable design with low maintenance costs and low environmental impact that generates long-term value to the building owner.

Great for the environment and easy to work with, InvariMatte® stainless steel is the perfect choice for beautiful, durable, energy-saving roofs.

InvariMatte® has a low glare texture which is easy on the eyes, even in direct sunlight, which makes it ideal for roofing applications. While it does have a muted appearance, there is just enough reflection going on to take on the colors of the environment around it. Looking bluish gray on a blue sky day, it takes on warm tones at sunset. InvariMatte® retains its original beauty over time without developing a patina. Its unique finish, which involves no coatings, is rolled directly into the surface of the metal. This process not only controls finish variability more closely than any other surface treatment available on bare metal, it also results in a visual effect that is extraordinary. The low gloss InvariMatte® finish is ideal for roofing applications, wall panels, coping and trim. Perfect for designs ranging from modern to historic renovations, its enduring beauty truly goes the distance.